I wouldn't feed them the mix; for one thing you are cutting the dosage which at best means you are not doing any good and at worst is helping build up resistance in the very things you are trying to avoid.
Secondly, I'm wondering why you put them on pine shavings after told not to. It just seems silly! lol I use puppy pads or paper towels for the first week or two then switch to newspaper covered in pine shavings. I buy the course shavings. At that point I expect they will eat a bit out of curiosity or while searching for stray crumble, so I put some grit in the food tray for them. I don't use straw except in nest boxes so no advice there. Pine shavings seem to work and should be okay for your keets at this point.
My advice: return to straw shavings (hopefully course), feed only the game bird starter, and make sure you have heat available for them somewhere in the brooder. Either a lamp or a heating pad.